Method of installing clinch staples

Abstract: A clinch type staple (22) has a U-shaped configuration with a pair of legs (26, 28) extending generally perpendicularly from a base portion (24) of the staple with the outside surface of the distal ends (30, 32) of the legs being bevelled. The legs of the staple lie in spaced apart planes that are parallel to one another, but are angularly offset from one another in order to insure that the legs (26, 28) will not contact or interfere with each other as they are clinched into a workpiece (34, 36). A plurality of such clinch staples (22) can be manufactured into an assembly (20) of clinch staples. The method of making such an assembly of clinch staples includes advancing a plurality of wires (42) in parallel side-by-side relation in a flat, planar array and adhering them to one another. A blank (54), severed from an end of the formed array, includes a plurality of side-by-side wire segments of equal length extending parallel to one another in a first direction. The severing of the wires is accomplished along a cutting line that is inclined by a bias angle (56) from a perpendicular to the first direction. The blank (54) is bent along two bending lines to form a channel-shaped stick of clinch staples with the legs (26, 28) extending perpendicularly from a base or bight portion (24) of the staples (22). The two bending lines are parallel to the cutting line so that the legs of the formed staples will be offset angularly from each other.

Description: The present invention relates to a method for installing staples from a staple assembly as specified in the pre-characterizing clause of claim 1. US-A-5 035 040 discloses a way of installing hog ring type fasteners around a wire or rod as, e.g., to attach upholstery material. In contrast thereto clinch staples may be used to fasten two or more workpieces together, one on top of the other, for example two strips of wood. In doing so, the legs of each of the staples are driven through the workpieces with the ends of the legs turned back or clinched into at least the lowest of the workpieces upon striking a flat metal anvil situated below. In order for the staple legs to be deflected inwardly or toward each other as they are driven into the workpieces, the outside surfaces of the distal ends of the legs are beveled. However, some provision must be made to assure that the legs are separated from one another as they are so deflected since, otherwise, they will contact or interfere with each other as they are being driven back into the workpieces after contacting the anvil. While oppositely directed, saw-toothed configured ends of the legs of clinch staples tend to insure that the legs will not interfere with each other as they are being clinched into workpieces, such staples cannot be readily and economically manufactured. Quite generally, a staple is a formed wire fastener having a generally U-shape configuration with parallel legs projecting perpendicularly from each end of a base or bight portion of the staple. In so far such staples could be economically fabricated and formed into assemblies of staples by means of automated manufacturing and packaging equipment. The staples that are the most economical to manufacture are those having points at the end of each leg that are formed by bevelling the end of the legs along planes perpendicular to the plane in which the base and legs of the staple lie. These points at the end of the staple legs are typically referred to as "C" points (a modified version of a "C" point - sometimes referred to as a "CO" point - results when only the outside surface of the end of the staple leg is beveled). However, problems occur when conventional clinch type staples having this type of modified "C" point or "CO" point are installed because the legs of the staples tend to contact or interfere with each other as the staples are being clinched into the workpieces. Staples can also be provided with offset points beveled in the transverse direction (typically referred to as a "D" point) so that the ends of adjacent legs within a corresponding staple assembly have a saw-toothed configuration. When, in this case, the saw-toothed ends are formed in opposite directions on each staple leg, the legs will be deflected from each other as they are being clinched into the workpieces and therefore will not interfere with each other. Unfortunately, the forming of such points requires a more expensive manufacturing process. Many staple type fasteners are made in a multi-wire process in which numerous wires are fed side-by-side in a flat plane to bonding, cutoff and forming stations. This is an economical and efficient process for producing staples with a "C" point where the ends of the staple legs are beveled generally perpendicular to the plane of the fastener. This type of point is formed by pinching off a blank from the flat array of adhered wires prior to forming the wires into the final U-shape configuration of the staple. The blank is rectangular and the legs are formed by bending the blank to make right angle corners perpendicular to the sides of the blank. However, saw-tooth, offset points at the ends of the staple legs cannot be readily formed using this manufacturing process and, consequently, this more economical manufacturing process has not been used for the manufacture of clinch type staples having "D" points. On the other hand, US-A-5 035 040 (as mentioned above) discloses a method for very economically manufacturing hog ring type fasteners having "C" or "CO" points and it has now been found that the same manufacturing method can be used for producing clinch staples for use in the way as claimed. Accordingly, the invention as claimed solves the problem of very economically manufactured clinch type staples which are secure in use. Though, according to the invention, the staple legs are offset from each other in order not to interfere as the staples are driven into the workpieces, these legs lie in parallel planes in order to attain the benefit of existing staple making and handling equipment. The staples include modified "C" or "CO" points and still their legs are adapted to move past each other as the staples are driven and clinched into workpieces. A staple for use according to the present invention has a U-shaped configuration with a pair of legs extending generally perpendicularly from a base or bight portion of the staple with the outside surfaces of the distal ends of the legs being beveled. The legs of the staples of a corresponding staple assembly lie in spaced apart planes that are parallel to one another, but the legs of each of the staples are angularly offset from one another in order to ensure that they will not contact or interfere with each other as they are clinched into the workpieces. As described in US-A-5 035 040, a plurality of such staples can be manufactured into a staple assembly by adhering the staples into a stick or strip of similar staples. Each of the staples is generally U-shaped having a base or bight portion and a pair of legs extending from the base. The bases of the staples lie in a first plane and the legs extending from the bases lie in second and third planes, the second and third planes being spaced apart from each other but parallel to one another and perpendicular to the first plane. In addition, the legs in the second plane are angularly offset from the legs in the third plane. In a preferred method of making such staple assemblies numerous wires are advanced in parallel side-by-side relation in a flat planar array and adhered to one another. A blank is severed from an end of the formed array, the blank including a number of side-by-side wire segments of equal length extending parallel to one another in a first direction. The blank then is bent along two bending lines to form a U- or channel-shaped stick of clinch staples with the legs extending perpendicularly from a base or bight portion of the staples. The severing step includes cutting the wire array along a cutting line that is inclined by a bias angle from a perpendicular to the first direction. In order that the legs of the formed staples are offset angularly from each other, the bending lines are parallel to the cutting line. For installation as clinch staples according to the present invention, after having been severed from a staple assembly one at a time, the staples are driven, legs ahead, into and through the workpieces previously positioned on an anvil. By striking the anvil the legs, due to the bevels at their distal ends, are deflected inwardly towards each other and back into at least the lowest one of the workpieces. However, the offset between the legs results in the legs crossing each other within the workpiece without contacting each other. Physically similar clinch staples are disclosed in DE-A-41 23 645. However, this document does not mention any type of corresponding staple assembly having legs of the staples offset with respect to each other. Moreover, these clinch staples are to be installed differently, without employment of an anvil. Their legs are not finally deflected back into one of the workpieces and thus these staples will not adhere very firmly. In the following a preferred manufacturing method of clinch staples for use according to the invention as well as their application is described in detail, taking reference to the accompanying drawings wherein: FIG. 1 is a side elevational view of an assembly of clinch staples for use in accordance with the present invention; FIG. 2 is a bottom view of the staple assembly of FIG. 1; FIG. 3 is a front elevational view of a single staple from the staple assembly of FIG. 1, taking generally from the line 3-3 of FIG. 1; FIG. 4 is a side elevational view of the staple of FIG. 3 taken from line 4-4 of FIG. 3; FIG. 5 is a schematic and diagrammatic view illustrating an arrangement for performing the preferred method of manufacturing the staple assembly of FIGS. 1 and 2; FIG. 6 is a fragmentary top plan view illustrating consecutive blanks cut in manufacturing the staple assembly of FIGS. 1 and 2; FIG. 7 is a perspective view of a staple driving tool for performing the method of the present invention, the tool being positioned relative to workpieces disposed on an anvil in order to drive staples from the staple assembly of FIGS. 1 and 2 into the workpieces; FIG. 8 is a partial, cross sectional view illustrating a staple as it is being driven into the workpieces by the driving tool illustrated in FIG. 7; FIG. 9 is a partial, cross sectional view showing the staple after it has been driven into the workpieces by the driving tool illustrated in FIG. 7; and FIG. 10 is another partial cross sectional view showing the staple of FIG. 9 driven into the workpieces. Referring now more specifically to FIGS. 1 and 2 of the drawings, a clinch fastener assembly 20 includes a plurality of similar clinch staples 22 constructed for use in accordance with the present invention. As is more readily seen in FIGS. 3 and 4 of the drawings, each staple 22 is a length of wire formed generally in a U-shaped configuration with a base or bight portion 24 and a pair of legs 26 and 28 having respective bevelled ends 30 and 32. The staple assembly 22 may be manufactured by the process described hereinafter in connection with FIGS. 5 and 6 of the drawings. The staple 22 is a clinch type staple that is adapted to be driven into workpieces, such as a pair of workpieces 34 and 36 illustrated in FIGS. 7-9, by a staple driving tool 38 (FIG. 7). When the staple 22 is driven into the workpieces 34 and 36, the ends 30 and 32 of the legs 26 and 28 impact against an anvil 40 because they are longer than the combined thickness of the workpieces 34 and 36. As a result of this impact and the bevelled ends 30 and 32, the legs 26 and 28 are deflected toward each other and turned back into the workpiece 36 thereby clinching or otherwise securing the legs 26 and 28 in the workpiece 36 such that the workpieces 34 and 36 are secured together by the staple 22. As will be discussed in more detail in connection with the method of manufacturing the staple assembly 20 illustrated in FIGS. 5 and 6, each of the staples 22 is formed from a length of wire into a generally U-shaped configuration with the legs 26 and 28 projecting perpendicularly from opposite ends of the base or bight portion 24. As is apparent from FIGS. 1-4, the legs 26 and 28 of the staples 22 lie in parallel planes (as viewed in FIG. 3), but the legs 26 and 28 are not parallel to each other. Instead the legs 26 and 28 project from the base 24 at a slightly different or offset angle 41 (FIG. 4). The offset angle 41 between the legs 26 and 28 is sufficiently large to assure that the legs 26 and 28 do not contact each other as they are driven into and through the workpieces 34 and 36 even though they are deflected inwardly or toward each other. The optimum size of the offset angle 41 between the legs 26 and 28 depends on the dimensions of the staple 22 and the wire from which it is made. A preferred range for the offset angle 41 may be from about one degree to about five degrees with a preferred offset angle 41 being about two degrees. It is common for clinch type staples with parallel or symmetrical legs to use oppositely directed "D" points to prevent interference between the staple legs as the staple is being driven into a workpiece. With this type of arrangement, points are cut on each of the legs so that a saw-tooth configuration is formed along each end of the legs of the staples of an assembly of staples . The saw-tooth ends on one side of the staples are directed in one direction along the length of the assembly while the other saw-tooth ends are directed in the opposite direction. However, such "D" points cannot be formed by simple cutoff tooling in a multi-wire process of the type described hereinafter in connection with FIGS. 5 and 6. To the contrary, the "D" points must be made as a practical manner by a more expensive process in which one wire at a time is severed and formed by cutoff tooling. In accordance with the present invention the distal ends 30 and 32 of the legs 26 and 28 are pointed and beveled on the outside surfaces of the legs. These configured leg ends 30 and 32 of the staples 22 are of a type known as modified "C" or "CO" points. The points of the opposed legs 26 and 28 are defined by two intersecting inclined planes running along the length of the ends 30 and 32 of the staples 22 when these are formed into the staple assembly 20. By using a modified "C" point at the ends 30 and 32, the staples 22 can be more readily and economically formed using the multi-wire fabrication process illustrated in FIGS. 5 and 6. Manufacturing of the staple assembly 20 as illustrated in FIGS. 5 and 6 is effected by a method that is both easily and economically accomplished. Preferably any conventional multi-wire staple manufacturing process can be modified in order to accomplish the manufacturing of the assembly of clinch type staples 20 disclosed herein. The process is begun by supplying a number of individual discrete wires 42 from a source or supply (not shown) in a flat planar, side-by-side array. The array of wires 42 is moved through an application station 44 where an adhesive or binder is applied to the array of wires 42. The adhesive usually is in a liquid form so that it can be readily applied to the array of wires 42. After the adhesive or binder is applied, the adhesive or binder needs to be dried or cured. Therefore, the array of wires 42 is fed through a drying or curing station 46 where heat, air or the like is applied to the array of wires 42. At this point in the fabrication of the staple assembly 20, each wire 42 is adhered to the adjacent wire or wires 42 such that a flat planar web or strip of wires 42 is formed (see FIG. 6). The web or strip of wires 42 then is advanced to a cutoff station 48 that includes cutoff blades or tools 50 and 52. The tools 50 and 52 are adapted to sever a blank 54 from the end of the adhered wires 42. The tools 50 and 52 are arranged at a bias angle 56 (see FIG. 6) offset from a line perpendicular to the direction in which the wires 42 extend. The bias angle 56 determines the leg offset angle 41 between the legs 26 and 28 of each staple 22 such that the leg offset angle 41 will be approximately twice the bias angle 56. Side edges 58 and 60 of the blank 54 are defined by and coincide with the direction or length of the wires 42. Ends 62 and 64 of the blank 54 are parallel to one another, but are angularly offset by the bias angle 56 from lines perpendicular to the side edges 58 and 60. Unlike in a conventional multi-wire process where a rectangular blank is severed at a cutoff station, the blank 54 of the present invention is of a non-rectangular parallelogram shape with opposed corners defined alternately by ninety degrees plus the bias angle 56 and ninety degrees minus the bias angle 56. After the blank 54 has been formed, it is conveyed to a forming station 66 (FIG. 5). The forming station 66 includes cooperating forming tools 68 and 70. When the tools 68 and 70 are closed onto the blank 54 the blank 54 is shaped into the assembly of fasteners 20. In this forming operation, corners 72 of the assembly 20 result where the legs 26 are deformed to extend from the bases 24 and corners 74 result where the legs 28 are deformed to extend from the opposite end of the bases 24. Once the forming operation has been completed, all of the legs 26 and 28 are of equal length and are in parallel planes. All of the legs 26 on one side of the assembly 20 lie in a first flat plane, all of the legs 28 on the other side of the assembly 20 lie in a second flat plane and all of the bases 24 lie in a third flat plane. The first and second planes are parallel to each other and are perpendicular to the third plane. The corners 72 and 74 are somewhat rounded or gradual and constitute right angle corners respectively between the first and third planes and between the second and third planes. In a conventional multi-wire fabrication process, the forming tooling is arranged so that its edges lie along lines perpendicular to the direction that the individual wires extend. In contrast, the tooling of the present invention, as is illustrated in FIG. 6, is arranged so that its edges extend along lines that are angularly offset by the bias angle 56 from a line perpendicular to the direction that the individual wires 42 extend and are parallel to the front edge 62 and the rear edge 64 of the blank 54. Unlike conventional staple assemblies made by known multi-wire fabrication techniques, the assembly 20 that is formed by the method illustrated in FIGS. 5 and 6 does not occupy a rectangular, right cylindrical volume. Instead, the legs 26 and 28 are canted or biased with respect to each other by the offset angle 41. The bias angle 56 between the side edges 58 and 60 of the blank 54 and the forming tools 68 and 70 causes the legs 26 and 28 to extend at different angles from the bases 24 to provide each individual fastener 22 with the offset angle 41 seen in FIG. 4. The assembly 20 is generally channel shaped with a longitudinal axis extending along the length of the assembly 20. Each leg 26 and 28 and each base 24 is angularly inclined with respect to this longitudinal axis. The staples 22 and the assembly 20 have significant advantages that are not achieved with known clinch type staples. One of these advantages is that they can be economically made with modified conventional multi-wire staple making equipment. Moreover, assemblies 20 can be handled and packaged at low cost by existing equipment used for other staples. Due in part to the fact that the planes of the legs 26 and 28 of the assemblies are parallel, the assemblies can be internested in dense and efficient packaging arrays. Once the assembly 20 is formed, it can be loaded into the staple driving tool 38. The staple driving tool 38 can be adapted from any standard type of staple driving tool. The particular staple driving tool 38 disclosed in FIG. 7 is a pneumatically actuated staple driving tool. The staple driving tool 38 includes a housing 76 with a rearwardly extending handle portion 78. An inlet 80 that is adapted to be coupled to a supply of compressed air (not shown) is disposed at a rear end 82 of the handle portion 78. The housing 76 also includes a nosepiece assembly 84 that is disposed at a front end 86 of the housing 76. A magazine 88 extending from the rear end 82 of the handle portion 78 to the nosepiece assembly 84 is adapted to receive the staple assembly 20 and to feed successive ones of the staples 22 into the nosepiece assembly 84 so that the successive staples 22 can be driven into the workpieces 34 and 36 by a driver blade 90. To accomodate the offset legs 26 and 28 of the staples 22 the nosepiece 84 can be provided with slots on either side (not shown). More specifically, the staple driving tool 38 is actuated by the depression of a trigger 92. When the trigger 92 is so actuated, compressed air provided through the inlet 80 is supplied to a drive cylinder (not shown) within the housing 76 to thereby drive the driver blade 90 downwardly in the housing 76 so that one of the staples 22 in the nosepiece 84 is driven into the workpieces 34 and 36 (see generally FIGS. 7-10). As the legs 26 and 28 of the staple 22 are driven through the workpiece 34, the legs 26 and 28 tend to deflect inwardly or toward each other due to the bevels on the outside surfaces of the ends 30 and 32 of the legs 26 and 28 respectively. The length of the legs 26 and 28 are sufficiently long that the ends 30 and 32 will be driven through both of the workpieces 34 and 36 and contact the anvil 40 on which the workpiece 36 is disposed. As the ends 30 and 32 penetrate through the second workpiece 36 and contact the anvil 40, the ends 30 and 32 are deflected upward into the workpiece 36 to thereby clinch the staple 22 in the workpiece 36. However, the legs 26 and 28 do not contact or interfere with each other due to the fact that they are offset from each other by the offset angle 41 and therefore deflect past each other. As a result, the workpieces 34 and 36 are firmly secured together by the staple 22.

Claims: A method for installing staples (22) from a staple assembly (20), said staple assembly including a plurality of such staples adhered together with each staple having a base portion (24) and first and second legs (26, 28) extending perpendicularly from said base portion yet offset at an offset angle (41) with respect to each other, the first legs (26) of the staples of said staple assembly (20) and the second legs (28) of the staples of said staple assembly lying in planes generally parallel to each other and each of said first staple legs (26) having a first bevel along the outside of its distal end (30) and each of said second staple legs (28) having a second bevel along the outside of its distal end (32), said method comprising removing said staples (22) from said staple assembly (20) one at a time for installation and being characterized in that it is performed employing said staples (22) as clinch staples for fastening together workpieces (34, 36) one on top of the other and, to this end, comprises the following additional steps: placing said workpieces (34, 36) on an anvil (40) and driving said removed staples (22), one at a time, into said workpieces (34, 36) by driving said first and second staple legs (26, 28) through said workpieces until their distal ends (30, 32) contact said anvil (40) and further until said base portion (24) of the respective staple gets rested on the top one (34) of said workpieces, whereby said bevels cause said distal ends (30, 32) of said staple legs (26, 28) to be deflected towards each other and back into at least the lowest one (36) of said workpieces with said staple legs crossing each other without contacting each other due to said offset. The method of claim 1, characterized in that said offset angle (41) of said staples (22) employed is between about 1 degree and about 5 degrees, and preferably about 2 degrees.

Inventors: KERRIGAN JAMES E, KERRIGAN, JAMES E.
Applicants: DUO FAST CORP, DUO-FAST CORPORATION
Application year: 1994
Main classification: F16B15
IPC codes: B27F7, F16B15, B25C5